Physiotherapists often need to assess a person's strength and range of motion in order to gauge the extent of a person's ability, rate of recovery, and the effectiveness of a particular physiotherapy regime.
Currently the assessment is based on functionality, e.g. the MRC scale for grading muscle strength, and is somewhat subjective. For example, one criterion is whether the subject can raise their forearm against the force of gravity. The subject will either be able to achieve this or not, although some credit is given for almost achieving it. A combination of simple tests of this kind combined with a subjective strength assessment obtained from physically resisting the subject's limbs through a range of motion leads to a score or index from 0 to 5 that describes the strength and functionality of the patient.
The advantage of this type of assessment is that it sums up a patient's ability in a single number. This can also be a disadvantage as it encompasses a number of criteria, hiding the subtleties of the subject's profile of abilities, and cannot be used as an accurate gauge of progress.
It is also known to use isokinetic dynamometers to measure muscle strength across the range of motion that a patient has. This is achieved by a torque sensor arm being driven in an arc by a variable speed motor. The patient pushes against the arm through the range of motion. A pair of graphs is produced that records torque and angle of the arm.
Other devices have also been developed to assist in the assessment of a person's strength and range of motion. For example, U.S. Pat. No. 6,792,801 describes a handheld apparatus that is capable of testing isometric muscle strength in one mode and range of motion in another mode.
It is an object of the present invention to provide an improved instrument for measuring the angles and forces associated with a joint of a person, or to at least provide the public with a useful choice.